Hey!
I'm trying to install a 1980 300 cylinder head on my 1979 block. All went good until I tried to rotate the crank to set the timing. My pistons are hitting the prechambers! I checked the prechamber height for 1980 specs, they are all at specs ( 8mm ). I noticed the 1979 head has flat tipped prechambers where as the 1980 head has round. I can't seem to find much info on this, does anyone know if there is a difference?

Thanks!

 

Very good thought, but the rocker arms are not installed yet and none of the valves will open until they are installed. ( glow plugs and injectors are out allowing crank rotation with all valves shut )
I removed the cylinder head this morning and found definite witness marks that the prechambers are hitting piston #1 and #4. I also noticed that the prechambers on the 79' motor appear shorter and flat compaird to the round 80' nozzles although I haven't been able to measure the flate 79' ones just yet.
The 1980 motor has EGR, but the 1979 did not. I wounder if they changed the prechambers the same year EGR was run. In that case, I might as well swap the later prechambers (80') for the earlier style (79') and measure for clearance this time to make sure they will clear.
After all is done, I can't wait to go cruisin' in the 300D!

 

Update,
There must be a difference in prechambers between the 5 cyl 300 1979 ( non egr ) and the 1980 ( egr ).

I ended up swapping the 1980 prechambers out for the 1979's to the head on the 1979 block/pistons. The nozzle height went from 8mm down to 5.5mm. Pistons are no longer hitting the prechambers and all is now clear.

Subtle diferences will always bite you in the ars if you don't have experience on a particular carline and model year. Live and learn...